1. Field of the Invention
The present invention relates to a signal processing circuit including a nonvolatile semiconductor memory device.
2. Description of the Related Art
A signal processing circuit such as a central processing unit (CPU) has a variety of configurations depending on its application but is generally provided with various semiconductor memory devices (hereinafter simply referred to as memory devices) such as a register and a cache memory as well as a main memory device for storing data or an instruction. In addition, a cache is provided in a CPU so as to be located between an arithmetic unit and a main memory device in order to reduce low-speed access to the main memory device and speed up the arithmetic processing.
It is necessary that a memory device such as a cache performs data writing at higher speed than that of a main memory device. Therefore, in general, a flip-flop is used as a register and an SRAM or the like is used as a cache. Further, Patent Document 1 discloses a structure in which a volatile memory such as an SRAM and a nonvolatile memory are used in combination as a cache.